Full vs. partial rewire

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  #1  
Old 08-03-02, 01:21 PM
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sequoia_s
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Question Full vs. partial rewire

I know this is supposed to be a DIY forum, but I was hoping somone can give me some unbiased info as we have a difference in recommendations between different electrical contractors on rewiring...

Our house was built in 1946. It has steel-flex conduit throughout, with cloth-insulated copper wiring. When we bought the house in 1999, we had the old electrical panel and meter replaced with a 200 amp panel and were advised that the wiring appeared to be in good shape. Somewhat later, I had an electrican out to troubleshoot a new ceiling fixture (circular fluorescent) I had installed but which would not work. The problem turned out to be a bad switch, but when the electrician checked the box for the fixture, he said that the insulation was badly deteriorated and the house should be rewired, with new wiring run through the existing (sound) steel flex.

More than a year later, I'm getting a home equity loan and getting bids for the rewire along with copper repipe replacing the 60+ year old galv. pipes, a new roll-up garage door/opener replacing the heavy old wood door, and a few other things.

I've had the same electrician come out to bid the job, along with the one who installed the panel (different outfit). I just had a 3rd electrical contractor come out to bid the job, and he said that I did NOT have to replace all the wiring and recommended that we have him replace only the wiring from the switches to the lighting fixtures, replace the old mercury switches, and replace the outlets with self-grounding outlets (this last was actually my request). We are also having whatever contractor we select do some additional work such as adding outlets and ceiling fans, but that is not at question here.

He said that the wiring to the outlets is not subjected to the same heat as wiring to the ceiling fixtures and thus does not deteriorate. He took the cover off of one of the outlets and check the wire to confirm/demonstrate. As far as I could tell, the instulation was/is indeed sound.

My question is: if indeed the wiring is sound to the outlets, should I save the $2000 or so difference between full and partial rewiring, or should I go with all new wiring a know that everything is new and sound (presuming whatever contractor I select does the job right)?

So far, all the contractors either come well recommended or have done work for me before and I believe I can trust them. Saving the $$ would be nice, but not if it compromises the safety of our house in any way.

Thank for your help.
 
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  #2  
Old 08-03-02, 01:45 PM
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I opt for new,,, a one shot deal and you cannot get grunding for recepts with that type of cable. It is not legit to use if for grounding conductor so the recepts you put in with 3 wire may be more dangerous than having 2 wire.
 
  #3  
Old 08-03-02, 01:47 PM
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Also,,, whats that cable going to look like in the next 20 years and loads are increasing all the time on wiring with more appliances.
 
  #4  
Old 08-04-02, 09:25 AM
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Another point to consider is that the wiring is "good" according to an electrician, he wants to make money. There is the chance that he is trying to get your job by telling you a cheaper way (i.e. getiing $2000 for a partial rewire is better than getting no $$ at all), but I doubt he would tell you not to do something if it were truly dangerous. You will probably have more money in the future so this job may be more affordable then, also the average time a homeowner spends in one house is around 7 years. If you don't think you will be in your house very long, just do lights/switches, if you really think you will be there a whil, it might be worthwhile to do the receptacles now.
Just a few more points to ponder.

Bob
 
  #5  
Old 08-05-02, 08:03 AM
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sequoia_s
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Thanks guys.

I doubt he is trying to mislead me, tho' it is quite feasible he is trying to be the low bidder on the job by doing less work.

Also, I have see that the insulation is sound on the old wire at the panel, and in some of the outlets I've replaced myself. Where it looked iffy was indeed at the ceiling fixtures. Even so, since our intent is to be in this house 'till the mortgage is paid (we refi'ed last year) I'm inclinded to go with Bob M.'s reasoning.

As far as the gounding, more than one electrican has said it IS acceptable to use self-grounding outlets with steel-flex conduit in a **replacement** situation (as opposed to new construction or installing new wiring). Even so, having a actual ground wire running through the conduit sounds like a better way to me as a layman.

Thanks again,

Sequoia
 
  #6  
Old 08-05-02, 03:07 PM
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bwetzel
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I would like to know what electrician is telling you it is ok to use flex to ground recpts. There is no flex out there that makes it ok. However, it is legal to replace a 2-wire recpt with a gfci as long as there is a sticker placed on the recpt stating there is no equip. ground. If they put new recpts. in make sure they ar GFCI protected.
 
  #7  
Old 08-07-02, 04:26 AM
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sequoia_s
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Exclamation Grounding through BX/AC

The "Electrical Wiring FAQ"
(http://www.landfield.com/faqs/electr...ection-33.html),
CodeCheck (http://www.codecheck.com/NEC_hnd_2pr...ommentary.html), and
Handyman USA (http://www.handymanusa.com/questions...q.html#outlets)
ALL state that you can ground to the box if you have a metal box and metal (including flex) conduit, IF the system is grounded and the box is grounded.

I know my system is grounded (armor-clad GEC runs from main panel to grounding rod nearby, which is also bonded to the plumbing) AND the conduit is all "Armor-clad" with metal boxes, providing a path for the ground all the way back to the panel. Therefore, according to the above sources, I can use the conduit to ground the receptacles by installing self-grounding outlets or connecting a ground wire from the green screw on the outlet to the metal of the box.
 
  #8  
Old 08-07-02, 07:04 AM
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No flex for grounding recepts. Look back a page or so,, a real long thread,, 40 or so responses and some deep digging by WGoodrich. Code says no flex over 6 feet without a grounding wire.
 
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Old 08-07-02, 09:42 AM
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Sequoia; Which of these two choices bests describes the Wiring Method in your house? -----1, Armored Cable which is a factory assembly of insulated conductors enclosed a metal sheath or 2, Flexible Metal Conduit which is a raceway in which the conductors are inserted by the person installing the FMC?------If you have Armored Cable then Art. 320.108 applies which reads-----"(the) Cable shall provide an adequate path for Equiptment Grounding----"-----Using the armor of FMC as an Equiptment Grounding Conductor depends on whether the FMC is "listed" or "not listed" for Grounding-Art. 250.118, Types of EGC's, (5),FMC listed for Grounding and (6), FMC not listed for Grounding.
 
  #10  
Old 08-07-02, 12:44 PM
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Wgoodrich
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COPIED SECTION OF NEC 2002;
320.100
III. Construction Specifications
320.100 Construction.
Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.

Patbaa, if you do not have the internal bonding strip of copper or aluminum in intimate cotact with the armor its entire length you do not have Armor cable.

Also if checked flexible metallic conduit FMC is not recognized as a grounding path in 3/8" size.

COPIED SECTION OF NEC 2002;
348.20 Size.
(A) Minimum. FMC less than metric designator 16 (trade size 1/2) shall not be used unless permitted in 348.20(A)(1) through (5) for metric designator 12 (trade size 3/8).
(1) For enclosing the leads of motors as permitted in 430.145(B)
(2) In lengths not in excess of 1.8 m (6 ft) for any of the following uses:
a. For utilization equipment
b. As part of a listed assembly
c. For tap connections to luminaires (lighting fixtures) as permitted in 410.67(C)
Section 348.20(A)(2) makes it clear that 3/8-in. flexible metal conduit is permitted to be used as the manufactured or field-installed metal raceway (11/2 ft to 6 ft in length) to enclose tap conductors between the outlet box and the terminal housing of recessed luminaires. Flexible metal conduit is also permitted to be used as a 6-ft fixture whip from an outlet box to a luminaire.
(3) For manufactured wiring systems as permitted in 604.6(A)
Section 604.6(A) permits a smaller minimum size for manufactured wiring systems because the conductors are not as prone to physical damage when assembled under factory-controlled conditions.
(4) In hoistways as permitted in 620.21(A)(1)
(5) As part of a listed assembly to connect wired luminaire (fixture) sections as permitted in 410.77(C)

COPIED SECTION OF NEC HANDBOOK 2002;
348.60
According to the product standard UL 1, Flexible Metal Electrical Conduit, FMC longer than 6 ft has not been judged to be suitable for grounding purposes. The general rules for permitting or not permitting flexible metal conduit for grounding purposes are found in 250.118(5) and (6). One specific exception is where FMC is used for flexibility. As stated in 348.60, an additional equipment grounding conductor is always required where FMC is used for flexibility. Examples of such installations include using flexible metal conduit to minimize the transmission of vibration from equipment such as motors or to provide flexibility for floodlights, spotlights, or other equipment that requires adjustment.
Another specific exception is the requirement for a bonding jumper where FMC is used in hazardous (classified) locations. See 501.16(B), 502.16(B), and 503.16(B) for details on types of equipment grounding conductors. In addition, 250.102(E) permits the routing of equipment bonding jumpers on the outside of the raceway in lengths that are no longer than 6 ft and bonded at each end.
According to 250.118(6), where the length of the total ground-fault return path exceeds 6 ft or the circuit overcurrent protection exceeds 20 amperes, a separate equipment grounding conductor must be installed with the circuit conductors. The sketch on the right in Exhibit 348.1 shows an acceptable application of flexible metal conduit where the total length of any ground return path is limited to 6 ft. The sketch on the bottom shows an application that is unacceptable because the grounding return path for luminaire 2 exceeds the permitted maximum of 6 ft to the box.

Wg
 
  #11  
Old 08-08-02, 06:51 AM
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sequoia_s
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Flex for grounding

The "Wiring Method" in my house is flexible metal conduit ("FMC"). Remember, the house was built in 1946 and the wiring is, for the most part, original. I have not specifically measured it, but I believe most, if not all of the conduit, is 3/4-inch diameter and I have been told it is steel, not aluminum.

Do the code sections you refer to pertain to 1) new construction; 2) wire replacement, or 3) fixture/outlet only replacement?

All 3 of the sources I cited earlier seem to strongly indicate that it is acceptable to use FMC for grounding when replacing existing outlets, not when installing new wiring.

As it turns out, I may in fact wind up replacing a number of the outlets and switches myself, as I may not be getting the equity loan I was hoping for, at least not with terms that are acceptable to me.
 
  #12  
Old 08-08-02, 07:00 AM
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If you have Flexible metal conduit then all of these conversations are mute!!!! When you install the new wires all they have to do is pull a grounding conductor in with the circuit conductors and you will have a ground that meets code.
 
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Old 08-08-02, 09:29 AM
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The basic purpose of an Equiptment Grounding Conductor such as the metal of armored cables and raceways is to form a low-resistance path for Ground-Fault currents which are conducted back to the point where the EGC is bonded to the Grounded System Conductor (the Neutral). From "a practical point of view" 1/2" (trade-size) FMC which encloses 15 amp Branch-Circuit conductors is superior to #14 Armored Cable as an EGC because of the difference in size of the metal armor and connectors. There is no "trade size" for Armored Cable- the diameter of the cable may vary.1/2" FMC which grounds 15 amp Branch-Circuits is similiar in size to #8/3 Armored Cable which must ground 40 amp circuits and the larger the Branch-Circuit rating, the larger the Ground-Fault current. Applying the Code retro-actively to existing conditions cannot be done with absolute certitude.
 
  #14  
Old 08-08-02, 10:01 AM
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Cool Grounding to FMC

Sparksone - The start of this whole thread was that one of the electricans bidding on the rewire proposed replacing only the wiring to the lighting fixtures, leaving the wiring to the outlets in place and installing self-grounding (not necessairly GFI) outlets.

It turns out I may not be able to have the rewire done at all, if I do not get the equity loan I need for the work at acceptable terms. In that case, I will be replacing outlets only as required, and after this whole conversation, I will probably replace most of the 2-prong (ungrounded) outlets with new 2-prong outlets.

BUT
1) I have installed 4 GFI's and 2 regular 3-prong outlets (in kitchen, not near sink or other water source) by "grounding to the box (I had to use a wood screw [if there was wood behind the box] or a 1/4" lag screw to connect to the unused nailing hole in the old boxes). The only grounded appliances that are actually plugged into these outlets are a) the microwave, and b) the power-center for my computer, printer, etc. both plugged into the GFI's.
and,
2) I would be inclined to install a few self-grounding (not GFI) 3-prong outlets throughout the house, mainly for electronics but also for occassional power-tool usage.

At this point, if I need a definitive answer on using the self-gounding outlets, I will probably check with the City of Los Angeles Building & Safety Dept., since this seems to be a "hot" controversy here!

Also, I could be wrong, but from my visual inspection I am pretty sure that the exisiting FMC is 3/4-inch, not 1/2-inch. This would not be out of character because the house was custom-built in 1946 and many features and components exceeded code requirements (of the time).

p.s. If I do get the loan and have the house rewired, I will almost certainly go ahead and have all the old wiring replaced and have them pull a grounding conductor through with the curcuit conductors.
 
  #15  
Old 08-08-02, 12:21 PM
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If you can do it why not push a green wire thru the flex where you need it? if it is 3/4 it doesnt seem a problem. The thing with the wood screw and the lag doesnt sound so good. If you hook the green to the outlet it will bond to the box when you reinstall it. Just make sure to take the little cardboard insulaters off the screws. Buy a roll of 12 green, 20$ and you have enought for a whole house. Get a roll of Black and White and replace anything in doubt at the same time.
 
  #16  
Old 08-08-02, 04:29 PM
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bwetzel
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What are you calling a self grounding outlet?? If the metal box or the duplex is not grounded, where does your ground come from? Here is your answer. If you are not willing to install a green wire in the flex, You must install a GFCI You can not change a two wire recpt to a three wire recpt with out an equipment ground. Exception: You can install a GFCI in place of the two wire recpt as long as it is marked "NO EQUIPTMENT GROUND". This sticker comes with the GFCI. As for the kitchen, You must install GFCI's on all counter recpt. even if it is not close to any water. The NEC now states "ALL KITCHEN COUNTER RECPT " must be GFCI protected. This should clear it up for you.
 
  #17  
Old 08-08-02, 09:22 PM
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Captain Avenger
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Not OK by the Captain

There is one thing that doesn't sit well with me in your original statement. You said, about the electrician,

"He said that the wiring to the outlets is not subjected to the same heat as wiring to the ceiling fixtures and thus does not deteriorate. He took the cover off of one of the outlets and..."

There is no way he could possibly affirm this. The wiring to the outlets IS subjected to heat, but IT ALL DEPENDS ON WHAT YOU PLUG IN TO THAT OUTLET. Maybe it is OK now, but what will you use on that outlet?

If you are using a hair dryer, that is going to heat up the wire. If you are using a vaccuum, that will heat up the wire. If you are plugging in an electric blanket, a coffee pot, (I don't know), all of these things affect the wiring to the outlet(s).

I tend to agree with Sberry. Go for new while you can. It makes sense if you will live here until you pay the mortgage, like you say.
Whatever you do I wish you the best with your home.


Captain Avenger

Please post back if you have any other questions
 
  #18  
Old 08-09-02, 11:54 AM
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Captain Avenger, I suspect the reference to heat at light fixtures is heat produced by the light bulbs not the wire. Heat from light bulbs have been a concern due to heat damage of the wires in close proximity to that light fixture mounting.

The measurement of FMC is measured from the inside diameter not the outside diameter. Go to an electrical supply store and look at 3/8" flex. You will probably find that you flexilbe metal jacket is that size being the older style BX cable.

If that is true you would not be able or allowed to pull a grouding conductor inside that BX cable. The older BX cable was a manufactured product with the metallic jacket installed with the conductors during the manufactured process. Not enough room to pull another conductor inside 3/8" metal jacket.

Measure you metallic jacket by the inside diameter not the outside diameter.

bwetzel is correct, a self grounding receptacle is only good connected to a metal box that is connected to a metal conduit or other approved grounding path.

You will also probably have a terrible trouble finding new two prong recepatcles also.

I know your desire is to save money invested. There is just no good easy answer to change two prong receptacles to three prong receptacles. This is why this subject is such an on going hot issue.

Wg
 
  #19  
Old 08-10-02, 08:58 AM
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sequoia_s
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2 and 3 wire outlets

Wgoodrich -- I will definitely measure the id of the FMC and get back to you (the same FMC was used, and abandoned, for telephone wiring and is cut in one accessible place so I can actually measure the id). The OD of the conduit is in fact larger than that of the armored cable I ususally see at Home Dope, etc. I'd be very surprised if the id was only 3/8".

Also, I think I've see 2-prong outlets at Home Dope and/or OSH, but I'm not sure ... I'll check on that as soon as work. As far as the boxes themselves being grounded, I would think they are since the FMC leads either to the panel or to other original metal boxes connected to the panel by FMC, and the panel is bonded (right term?) to the grounding rod by armor-clad GEC. Whether that grounding connection (i.e., the FMC) is adequate to ground outlets seems to have been the subject of this entire thread (& others).

I still intent to check w/ L.A. City B&S for an opinon on using "self-grounding" outlets.

I am puzzled though, but one thing:

Most of the outlets sold, even for replacement, are in fact 3-prong, "grounded" outlets. However, most of the appliances, lighting, etc. used in a modern U.S. home have, in fact, regular or double-insulated TWO-WIRE cords and plugs. The only exceptions I can think of are Refigirators, Microwave ovens, computers, monitors, and hair dryers. Even most of my power tools have 2-wire double-insulated cords, including fairly heavy-duty tools from Bosch and Mikata. Same for my fairly light-duty garden tools. The 25-ft. long (and longer) HD extension cords, on the other hand, are almost universally 3-prong ... one has a real hard time finding a 2-prong heavy-duty extension cord.

Anyway, why the big push for grounded outlets if most of the applicanes we use are double insulated and don't need a 3-prong receptacle? If it were not for the extension cords (and power-strips), in my home we could get away without grounded outlets (or adapters) except in the garage (which does already have properly installed grounded outlets, albiet too few), the kitchen, and wherever we put the computer (current the kitchen).

Kinda curious.

- Sequoia
 
  #20  
Old 08-10-02, 12:52 PM
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Wgoodrich
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Sequoia, I think you answered your own question is you reread what you said.

While it is true most lamps, TVs etc. are two prong plugs without a third prong being a grouding prong as accepted and recognized in the NEC, this is only for those types of small appuratuses.

Large appliances, and many other convenience tools and equipment plugged into the house during normal use such as computers, washers, etc. have large amounts of metal in the casings and shells or sensitive electronic equipment.

While we have lived for decades with houses with only two wire systems without an equipment grounding system, we have discovered over the years too many injuries due to shock from large appliances with large metal shells or casings. Then we have electronic equipment that can be blown out just be the human hand touching the C-Boards in computers etc. due to very small charges of static electricity in our bodies that discharged into the C-Boards of electronic equipment when we touched them. The equipment grounding conductor often can obsorb those surges protecting sensitive electronic equipmnent from failure due to those surges.

Due to the ever changing and increasing demaind of the electronic equipment and the history of injury due to electrical shock from shorted large appliances such as refrigerators, washer and the like the equipment grounding conductor and equipment grounidng system was introduced. The future seems to show a demand for the need of the equipment grounding conductor and sytem more and more as the years go by.

If a person owns a older home that was wired and met a previous NEC version from the past then forever it be accepted as existing in the older NEC version that still makes that older two wire non grounding style wiring design in that older home. However now we have the equipment grounding system using three prong receptacles. People have grown to rely on this three prong receptacle connected with an approved equipment grounding path. When a person just changes a two prong receptacle to the three prong receptacle without installing a new grounding conductor to the panel from that new three prong receptacle or installing GFI pretection, or replacing the entire branch circuit with a three wire branch circuit then we have created a trap inviting a false beleif that three prong receptacle is with an equipment ground when it is not.

The new large appliances have changed their wiring design that has separated the neutral and the grounding creating the large appliance design expecting that grounding conductor to serve that large appliance from teh main panel as new wiring.

Now we have an older house with new large appliances other than just table lamps, shavers and the like designed to rely on an equipment grounding conductor that isn't in the system.

If you have an older home although it is a pain and expensive to upgrade from a two wire system design to rewire the entire home to a new three wire system design your money would be well spent not only in your family's increased safety but also resale value when you sell you older home with a complete new up to date wiring system that meets today's code.

Put yourself in position as a buyer of a older home. Would you pay more for an up to date wiring system?

Then again put yourself in a older home that has served you for decades without someone being hurt, would you stand to have those powers at be demand that you rewire your home.

We have a quandry that is not only expensive but very time consuming and extensive to rewire an older home to today's wiring style. Yet if all facts were considered the easy way is not the best or safest way for your families' future or your future resale of your home.

Good Luck and hope this helped

Wg
 
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